1. Field of the Invention
The present invention relates to a semiconductor device and, more particularly, to a semiconductor device arranged such that the semiconductor chip is mounted on a tape carrier by a TAB (Tape Automated Bonding) method and the heat radiating performance is improved.
2. Description of the Related Art
FIGS. 11A and 11B illustrate a tape carrier on which a semiconductor chip is mounted. The tape carrier includes a tape base material 1 formed in a film-like shape. The tape base material 1 is made of an insulating material, such as a epoxy resin in which a glass fiber is embedded, polyethylene, or polyimide. This tape base material 1 is provided with a plurality of perforations 5 along the two side edges thereof at equal intervals, and is further provided with a rectangular center device hole 3 in a central portion thereof for the purpose of accommodating a semiconductor chip 2. The portions surrounding the center device hole 3 are provided with a plurality of outer lead holes 4. A plurality of leads 7 made of copper are secured to the upper surface of this base material 1. These leads 7 are supported by a support portion 6 disposed between the center device hole 3 and the outer lead holes 4. The front portions of these leads 7 project as inner leads 7a into the center device hole 3, while the intermediate portions which serve as outer leads 7b to be connected to the electrodes of an outer circuit, are positioned above the outer lead holes 4. The rear portions of the leads 7 are provided with test pads 7c. The support portion 6 is connected to the tape base material 1 with bridge portions 6a disposed between the neighboring outer lead holes 4. As shown in FIG. 11B, in the center device hole 3, bump electrodes 21 of the semiconductor chip 2 are connected to the inner leads 7a of the leads 7.
The semiconductor chip 2 mounted on the tape carrier as described above is molded in a package, for example, of a type shown in FIGS. 12A and 12B. The semiconductor chip 2 is accommodated in an electrically conductive cap 8 such that the lower surface thereof and the electrically conductive cap 8 are joined by soldering or an electrically conductive adhesive 9. The electrically conductive cap 8 is provided with a flange 8a in the peripheral portion thereof, the support portion 6 of the tape carrier being supported on this flange 8a. Resin such as an epoxy resin or the like is supplied to the inside of the electrically conductive cap 8 and on the upper surface of the tape carrier so that a main package body 10 of the semiconductor chip 2 is formed. The leads 7 are then cut at the positions between the outer leads 7b and the test pads 7c, and the bridge portions 6a of the tape base material 1 are cut. As a result, a semiconductor device is formed.
The above-described electrically conductive cap 8 serves as a lead when a certain potential needs to be applied to the reverse side of the semiconductor chip 2 and serves as a heat radiating means for radiating heat generated in the operating semiconductor chip 2.
Recently, the radiation from the semiconductor chip 2 has been increased in accordance with a tendency toward higher density and higher speed semiconductor devices. Therefore, in order to improve the heat radiating performance of a semiconductor device, a semiconductor device of the type employed is arranged such that heat radiating fins 11 are secured, as shown in FIGS. 13A and 13B, to the reverse side of the electrically conductive cap 8 by solder 12 or an electrically conductive adhesive.
However, the semiconductor device shown in FIGS. 13A and 13B suffers from deterioration in heat radiating performance due to a resistance to heat conduction caused from contact of four types of layers consisting of an electrically conductive adhesive 9, the electrically conductive cap 8, the solder 12, and the heat radiating fins 11 which are present between the lower surface of the semiconductor chip 2 and the outside thereof.
Furthermore, the thickness of the resin on the upper surface of the semiconductor chip 2 for the purpose of forming the main package body 10 cannot be made sufficiently thin since the package needs to maintain its predetermined strength and reliability. This leads to the fact that the heat radiation from the upper surface of the semiconductor chip 2 is insufficient.
As described above, the conventional semiconductor devices manufactured by the TAB method suffer from poor heat radiating performance.